Project Summary Type 2 diabetes affects 9.4% of US adults with higher rates among racial/ethnic minorities and individuals of low socioeconomic status. The National Diabetes Prevention Program (NDPP) is an evidence-based and widely disseminated behavioral intervention to reduce diabetes incidence through modest weight loss. However, retention in the yearlong NDPP is problematic and leads to suboptimal weight loss, especially among Hispanic, non-Hispanic black, and low-income non-Hispanic white participants. Strategies to improve NDPP engagement and weight loss are needed urgently, especially for these subgroups. Pilot results of the Pre- NDPP, a novel enhancement to enrollment in the NDPP based on the Health Belief Model, were highly successful in a non-randomized cohort study among 1,140 racially diverse, predominately low-income participants. Outcomes of 75 Pre-NDPP participants who enrolled in the NDPP were compared to 1,065 prior participants using ANCOVA and multivariable logistic regression. Pre-session participants stayed in the NDPP 99.8 days longer (p<.001) and attended 14.3% more sessions (p<.001) on average than those without a pre- session. Pre-session participants lost 2.0% more weight (p<.001) and were 3.5 times more likely to achieve the 5% weight loss target (p<.001). Sensitivity analyses were consistent. Findings suggest pre-sessions may be a promising and pragmatic strategy to improve NDPP effectiveness and mitigate disparities in program outcomes, but a randomized controlled trial (RCT) is needed to determine whether Pre-NDPP reliably improves NDPP outcomes. The purpose of this study is to 1) conduct an RCT comparing NDPP attendance and weight loss outcomes between participants who receive Pre-NDPP vs. direct enrollment into the NDPP (usual care), 2) examine potential effect mediators (perceived risk for developing diabetes and self-efficacy and readiness for weight control) and moderators (race/ethnicity and income level), and 3) evaluate implementation factors, including cost and projected return on investment. The long-term goal is to disseminate a scalable, evidence-based strategy to improve success of the NDPP and reduce disparities in NDPP effectiveness. If found to be effective, Pre-NDPP can be disseminated to all NDPP providers, including more than 1,700 NDPP sites, and may be supported by current NDPP payers such as Medicare, commercial insurers, and employer groups. Thus, this approach has a high potential to impact the burden of type 2 diabetes and related health disparities across the country.